Electrical appabattts



Feb. 14, 1933. A. 5. MANC|B 1,897,134

ELECTRICAL APPARATUS Filed Oct. 16, 1930 @y lMM W25 Patented Feb. 14,1933 UNITED STATES PATENT OFFICE ALVIN S. MANCIB, 0F SOMEBVILLE,MASSACHUSETTS, ASSIGNOB. TO JAMES S. SIYSEB, OF BRIGHTON, MASSACHUSETTSELECTRICAL APPARATUS Application led October 16, 1930. Serial No.489,058.

This invention pertains to. electrical apparatus and relates moreparticularly to means for regulating, controlling, or indicating theoperation of electrically energized apparatus or electrical apparatus ofany type. I am aware of certain desirable and useful apparatus of thistype previously devised, wherein two electric motors are differentiallyassociated with a movable element in such a manner that the rate anddirection of movement of the movable elements are directly related tothe difference in speed of the two motors.

As herein disclosed by Way of example, the invention is embodied inarc-welding apparatus comprising a motor driven feed roll for advancingor retracting the electrode, the improved construction being such as toinsure the provision of ample power in the motor for moving the feedroll and consequently the electrode, great stability in the motion `ofthe electrode since itsmovements are very positive both in magnitude.and directlon; to provide for great flexibility of operation since itpermits regulation of the arc length to maintain constant arc voltageunder any operating conditions; to permitthe use of heavy electrodes foruse with heavy currents such as are necessaryv under certam conditions;to permit employment of standard equipment, thus keeping cost ofproductionl at a minimum; and at the same time being capable ofembodiment in a simple construction.

The drawing consistsA of a diagram illustrating the circuit of myinvention.

The apparatus illustrated 1s specifically designed for arc welding,although it 1s clear that it may be used for controlling devices otherthan arc-welding devices, particularly where a constant potential isdesired between two points in a circuit. As shown, the movable element 1(the electrode), connected 1n the controlled or welding circuit, ismoved toward or from the work 2 by rotation of the shaft of motor 3.This may be accomplished by direct connection, ,or preferably through asystem of gearing permitting the motor shaft to make several rotationscorresponding to a small movement of the electrode.

The armature 4 of motor 3 is in series with the armature 5 of acontrolling motor 6 of the controlling circuit which is fed by powersupply lines 7 and 8. Motor 3 is supplied with afield 9 connected acrossthe same supply circuit in any desired manner, a separately excitedfield being found preferable. A second control motor 10 has its rotordirectly connected to the rotor of control motor 6 by means of acoupling 11, as shown, or any other desirable connecting means, forexample, gearing or belting or by being mounted on a single shaft. Thearmature of motor 10 is connected directly across the supply circuitcomprising lines 7 and 8. The motors 6 and 10 have fields indicated at13 and 14 respectively, which are fed from the supply circuit, eachfield preferably being connected as a shunt field. Either or both ofthese fields may have a rheostat or other means for varying the currentand thereby varying the field, rheostats 15 and 16 being illustrative ofsuch devices. In addition to the` field 1-3 of the motor 6 there is anauxiliary field 17 which is connected in the welding circuit and iscumulative with respect to the field 13. This connection preferably isconnected in parallel with the arc to obtain the most satisfactoryresults.

Since the field 9 is separately excited and does not change, it will beclear that the rotation of the armature of motor 3, and accordingly thedirection of motion of the movable welding element 1, will depend uponwhich way the current flows through the rotor of motor 3. When fieldwindings 13 and 14 furnish the same excitation to their respectivearmatures, there will be no opposed torque on the shaft which connectsthem. When the effective strength of the field of motor 6 is changed byvarying the strength of field 17, one of the motors 6 or 10 having theweaker field will drive the other as a nerator. Thus, it will be seenthat the unit having the stronger field will act as, a dynamic break toprevent excessive changes in speed.

Starting with electrode 1 out of contact with the work 2, before the archas been formed, the potential between them will be that of the weldinggenerator on open circuit. The auxiliary winding 17 will then have itsmaximum excitation and the motor 6. because of its stronger field, willbe operating as athrough the armature 5 of motor 6 and accordinglythrough the armature of motor 3 is reversed, causing the direction ofmovement of electrode 1 to cha-nge so as to withdraw it from the work.As soon as this happens the arc elongates and the increased voltage andresistance at the arc causes current to flow through the field 17, whichcurrent increases as the arc lengthens. Two agencies contribute totheincrease in arc length, one being the retracting movement of the feedroll, and the-other the fusion of the electrode in the arc. The former`vvillebecome less effectiveias the excitation in 17 increases, and themotor 3 will revolve more/and more slowly in the electrode retractingdirection until it comes to rest. However, continued lengthening of thearc, due to fusion, will result in strengthening the field of motor 6until current is caused to iow through the armature of motor 3 in theopposite direction and the electrode will start to' feed toward thework. The welding operation thus becomes continuous, the electrodeadvancing steadily toward the work at the same rate that it is consumedin the arc. By providing a rheostat in the main winding of either motor6 or motor 40 10, a means for manually varying the field of these motorsis provided, and by varying the field strength the eifect of theauxiliary field can be increased or decreased. This results in either alengthening or a shortening of the arc, so that an arc of any desiredpotential may be maintained.

It is thus evident that after having adjusted the rheostat for a givenarc potential, such potential is substantially maintained,

after the arc has been struck, due to the fact that thepotential acrossthe arc gap is dependent upon the position of the movable lelectrode,While the position of the electrode is determined in response to thepotential across the arc gap.

It should be understood that the present -disclosure is for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

ll claim:

1. Apparatus of the class described comprising a movable part whoseposition determines the potential in an electrical circuit, a

motor for moving said part, said` motor having a rotor and a separatelyexcited field, and a motor-generator set adapted alternatively to supplycurrent in opposite directions respectively to the rotor of saidfirstmotor, whereby to cause the latter to advance or retract said movablepart. Y

2. Apparatus of the class described coniprising a movable part Whoseposition determines the potential in an electrical circuit, a motor formoving said part, said motor having a rotor and a separately excitedfield, and a pair of control motors having mechanically connectedrotors, one at least of said control motors being in series with therotor of the rst motor, one of said control motors having an auxiliarylield so connected with the circuit whose potential is determined bysaid movable part as to vary in intensity in accordance with theposition of said part.

3. In a device of the character described, a movable resistance varyingelement in a circuit, a motor actuating said element, a control motorhaving its rotor in series connection with the rotor of the first motor,an auxiliary field Winding for said control motor connected in thecircuit for said movable element, and a second control motor having itsshaft directly connected to the shaft of said first control motor.

4. In a device of the character described, a movable resistance varyingelement in an electrical circuit, a motor actuating said element, a airof control motors having their shafts irectly connected together, one ofsaid control motors having arrauxiliary ield energized by the circuitfor said movable element, one of said control motors having its armaturein series with the armature of said irst motor, and means for varyingthe strength of the main field of one of said control motors.

5. In a device of the character described, a movable resistance varyingelement in an electrical circuit, a motor actuating said element, acontrol lmotor having its armature in series connection with thearmature of the first motor, an auxiliary field for said control motorin parallel with the resistance, and a second control motor havingitsshaft directly connected to the shaft of said first control motor.

6. In a device of the character described, a movable resistance varyingelement in an electrical circuit, a motor actuating said element, acontrol motor having its armature in le tors, and means for .varying theeffective `ingly to change the normal position strength of the field 'ofone of said control motors relatively to that of the other controlmotor.

8. An electric arc-welding device, a pair of electrodes, one at least ofwhich is movable, and means to maintain an arcof constant potentialtween said electrodes, said means comp an electrode motor for moving oneelectrode, means to determine the direction of rotation of said motor,said latter means com rising \two controlmotors havin vtheir aftsconnected together, one of said control motors having an auxiliaryfieldv in parallel with said arc, and one of said motors having itsamature in series with the armature of said first motor, and means formanually adjusting the strength of the main iield of one of the fcontrolmotors relatively to that of the other so as to change the eect of theauxiliary field at will, whereby the current strength in the armature ofthe electrode\motor is so changed as correspondof the electrode. f

g, 9. An electrical control system of the character described comprisina controlled circuit including a movable ement whose position determinesthe resistancein said circuit, a controlling circuit having amotor-generator set connected therein, said motor generator set havingan auxiliary field whose strength varies in accordance with the posi-.tion of said movable element, variations in the stre of saidauxiliaryieldproduc'- ing electrical uctuations in said controlling circuit, andelectromagnetic means for actu- 'ating said movable element, said meansbeing so connected in said controlling circuit as to be nsive to saidfluctuations.

10. An electrical control system of the character described com rising acontrolled circuit including a mov le-resistance varying element-acontrolling circuit including a motor-generator set an auxiliaryeldsoconnectedinthe contro edcircuitthat its `strength varies inaccordance with the variations in resistance in said controlled circuit,variations ingthe strength of said auxiliary field producing electricaluctuations in` said controlling circuit, and a motor for actuating saidresistance va 'ng element, said motor being so connec in saidcontrolling circuit as tobe responsive to said electrical fluctuations.

11. An electrical 4control system compriaing a controlled circuit inclua movable elementwhose 'tion determines the potential in said circuit, acontrolling circuit, a motor-generator set adapted to supply currentalternatively in opposite directions to said controlling circuit, saidmotor-generator set having an auxiliarv iield so connected in saidcontrolled circuit that its strength varies in accordance withvariations in potential in said controlled circuit, variations in thestrength of said auxiliary field causing fluctuations in current in saidcontrolling circuit, and a motorv for actuating said movable element,said motor being connected in l said controlling circuit and responsiveto fluctuations in current therein.

12. Welding apparatus com rising a welding circuit including relativeFymovable arc electrodes, a controlling circuit, a motorgenerater setadapted to supply current alternatively in opposite directions to saidcontrolling circuit, said motor-generator set having an auxiliary fieldso connected in said welding circuit that its strength varies vinaccordance with variations in the relative positions of said electrodes,variations in the strength of said aum'liary field producingfluctuations in current in said controlli circuit, and a motor formoving one of sai electrodes, said motor having a substantially constantield and having its armature connected in series in said controllingcircuit and responsive to fluctuations in current therein.

Signed by me at Boston, Massachusetts, this 14th day of October, 1930.

:i ALVIN S. MANCIB.

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